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VHIVEBSITT  OF  CALIFOBNIA  PUBLICATIONS 


COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA 


ALMOND  POLLINATION 


BY 
WARREN  P.  TUFTS  AND  GUY  L.  PHILP 


BULLETIN  346 

July,  1922 


UNIVERSITY  OF  CALIFORNIA  PRESS 

BERKELEY,  CALIFORNIA 

1022 


David  P.  Barrows,  President  of  the  University. 

EXPERIMENT  STATION  STAFF 
HEADS  OP  DIVISIONS 

Thomas  Forsyth  Hunt,  Dean, 

Edward  J.  Wickson,  Horticulture  (Emeritus). 

,  Director  of  Resident  Instruction 

C.  M.  Harino,  Veterinary  Science,  Director  of  Agricultural  Experiment  Station. 

B.  H.  Crocheron,  Director  of  Agricultural  Extension. 

C.  B.   Hutchison,  Plant   Breeding,   Director  of  the  Branch  of   the   College  of 

Agriculture  at  Davis. 
H.  J.  Webber,  Subtropical  Horticulture,  Director  of  Citrus  Experiment  Station. 
William  A.  Setchell,  Botany. 
Myeb  E.  Jaffa,  Nutrition. 
Ralph  E.  Smith,  Plant  Pathology. 
John  W.  Gilmore,  Agronomy. 
Charles  F.  Shaw,  Soil  Technology. 
John  W.  Gregg,  Landscape  Gardening  and  Floriculture. 
Frederic  T.  Bioletti,  Viticulture  and  Fruit  Products. 
Warren  T.  Clarke,  Agricultural  Extension. 
Ernest  B.  Babcock,  Genetics. 
Gordon  H.  True,  Animal  Husbandry. 
Walter  Mulford,  Forestry. 

James  T.  Barrett,  Plant  Pathology.  > 

Fritz  W.  Woll,  Animal  Nutrition. 
W.  P.  Kelley,  Agricultural  Chemistry. 
H.  J.  QuAYLE,  Entomology. 
Elwood  Mead,  Rural  Institutions. 
H.  S.  Reed,  Plant  Physiology. 
L.  D.  Batchelor,  Orchard  Management. 
W.  L.  Howard,  Pomology. 
*Frank  Adams,  Irrigation  Investigations. 

C.  L.  ROADHOUSE,  Dairy  Industry. 
R.  L.  Adams,  Farm  Management. 

W.  B,  Herms,  Entomology  and  Parasitology. 
John  E.  Dougherty,  Poultry  Husbandry. 

D.  R.  HoAGLAND,  Plant  Nutrition. 
G.  H.  Hart,  Veterinary  Science. 

L.  J.  Fletcher,  Agricultural  Engineering. 
Edwin  C.  Voobhies,  Assistant  to  the  Dean. 

■      •-...-...     f>J'WISION  .OF. -POMjQLPGY     .      .... 

W.  L.*  HoWitRl)  •  '••     •     'F- •'VCr!' ^Ujlen  •  ••    •    "•'    ■Oi 'iC. 'AtrsTiN 
-^-.-•P.  .TUJTJB.::     I    .♦.  -3";  P,;BqN^•BTy.:   .,      .«,  L.  H,  Da^ 
B.  X.  .Xy'^jjirfoiisSfe   •    i,  •  .K  Jj'  Phicp-'  :•*  I''  ''^    »,  if.*  J.*IIetp{Jer 
A.  H.  Hendrickson  W.  P.  Duruz  E.  M.  Russ 

L.  C.  Barnard 


*  In  cooperation  with  Division  of  Agricnltural  Knginepring,  Bnrenu  of  Public  Roads,  U.  S. 
Department  of  Agriculture. 


ALMOND  POLLINATION^ 

By  warren  p.  TUFTS  and  GUY  L.  PHILP 


1^  For  the  successful  production  of  orchard  crops  certain  important 

^  limiting  factors  are  to  be  considered.  In  the  culture  of  the  almond, 
^  freedom  from  late  spring  frosts,  a  deep  well-drained  soil,  and  the 
^         interplanting  of  proper  varieties  to  secure  cross-pollination  are  the 

chief  "limiters." 

Q  Almonds  were  planted  in  California  as  early  as  1853,  but  records 

show  that  the  tonnage  of  the  early  orchards  was  very  variable.     The 

V)        failure  was  due  largely  to  a  lack  of  knowledge  of  the  factors  con- 

0        trolling  the  successful  production  of  the  almond.    Gradually  it  became 

recognized  that  the  almond,  on  account  of  its  early  blooming  habit 

,  (in  certain  sections  of  California  sometimes  as  early  as  late  January), 

-Q       and  its  aversion  to  heavy  and  poorly-drained  soils,  would  succeed 

v6       commercially  only  in  certain  locations,  that  is,  where  there  is  little 

I        danger  from  late  spring  frosts  and  where  the  soil  is  deep  and  well 

drained. 

That  there  is  a  distinct  pollination  problem  with  the  almond  was 

"^       recognized  as  early  as  1885,  when  Mr.  A.  T.  Hatch,^  of  Suisun,  Cali- 

Jo    fomia,  pointed  out  the  fact  that  Languedoc  trees  near  seedlings  always 

\^      produced  heavier  crops  than  when  planted  in  solid  blocks.    On  account 

>.        of  its  reputation  for  light  bearing  the  Languedoc  variety  was  rapidly 

\      displaced  by  the  Nonpareil,  I.  X.  L.,  and  Ne  Plus  Ultra  varieties, 

i^    seedlings  originated  and  introduced  by  Mr.  Hatch  in  the  early  90 's. 

^      Many  of  the  later  orchards  were  also  planted  in  unsuitable  places, 

there  being  a  feeling  that  these  new  improved  varieties  would  prove 

profitable  under  all  conditions.     In  addition  to  the  failure  of  the 

orchards  planted  in  unfavorable  locations,  many  instances*  are  on 

record  as  to  the  non-bearing  of  the  Hatch  varieties  where  the  only 

plausible  explanation  is  that  of  lack  of  proper  cross-pollination. 


1  This  paper  is  a  final  report  of  the  work  of  which  a  preliminary  account  was 
given  in  California  Agricultural  Experiment  Station  Bulletin  No.  306,  Almond 
Pollination,  by  W.  P.  Tufts,  March,  1919.  In  many  particulars  this  article  is 
identical  with  the  earlier  publication,  but  contains  considerable  additional  data 
which  confirm  and  strengthen  the  findings  of  the  station  concerning  the  pollination 
problem  of  the  almond. 

2  California  State  Board  of  Horticulture  Reports,  1885-1886,  p.  326. 

3  Dargitz,  J.  P.,  Pacific  Rural  Press,  Vol.  72,  No.  10,  Sept.  8,  1906. 


235278 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


THE    PROBLEMS    OF    ALMOND    POLLINATION 

An  attempt  has  been  made  to  solve  the  following  problems  for 
California  conditions : 

1.  Self -fertility.* — What  varieties  of  almonds  grown  commercially 
in  California  will  be  profitable  when  planted  in  solid  blocks,  i.e.,  with- 
out pollenizers.? 

2.  Self-sterility^ — What  varieties  planted  in  solid  blocks  will  not 
be  profitable? 

3.  Inter- fertility. — If  the  commercial  varieties  of  almonds  at  pres- 
ent grown  in  California  will  not  produce  profitably  unless  cross- 
pollination  is  provided,  which  varieties  should  be  planted  together? 

Even  though  two  varieties  may  be  inter-fertile,  the  following  points 
should  always  be  considered  in  selecting  poUenizing  varieties: 

(a)   Commercial  value  of  the  pollenizer. 

(&)  Coincidence  of  bloom  of  the  pollenizer  with  the  variety  to  be 
pollinated. 

(c)  Succession  of  the  ripening  of  varieties  for  convenience  in  har- 
vesting. 

(d)  Amount  of  pollen  produced  by  the  pollenizer. 

(e)  Germinability  of  the  pollen  produced  by  the  pollenizer. 

ORGANIZATION    OF  THE   WORK 

The  methods  employed  for  the  solution  of  the  problems  just  out- 
lined were  those  commonly  in  use  in  cross-pollination  experiments. 
Briefly  stated,  this  part  of  the  work  consisted  in  the  application  by 
hand  of  the  pollen  desired,  having  first  removed  the  flowers'  own 
pollen-producing  organs  (the  stamens).  The  introduction  of  foreign 
pollen  through  the  agency  of  wind  and  insects  was  prevented  by  cover- 
ing the  hand-pollinated  blossoms  with  paper  sacks.^  Accurate  counts 
of  flowers  of  the  various  varieties  thus  treated  with  pollen  of  different 
kinds  were  recorded.  Later  in  the  season  the  sacks  were  removed. 
The  fruits  resulting  from  these  artificial  pollinations  were  counted 
and  the  proper  records  made  after  the  first  and  second  drops  and 
again  at  harvest. 

*  The  writers  prefer  the  terms  ' '  barren ' '  and  ' '  fruitful ' '  as  explained  by 
Kraus  in  the  Journal  of  Heredity,  Vol.  6,  No.  12,  pp.  549-557,  rather  than  the 
inexact  terms,  * '  sterile ' '  and  ' '  fertile. ' '  The  latter  terms  have  been  used  in 
this  paper,  however,  because,  as  herein  used,  they  are  more  or  less  familiar  to  the 
general  public. 

s  The  use  of  paper  sacks  is  probably  unnecessary.  In  fruits  like  the  almond 
there  is  practically  no  wind  pollination  and  insects  do  not  visit  emasculated 
flowers. 


Bulletin  346J  ALMOND  POLLINATION  5 

During  1910  the  work  was  carried  on  by  B.  S.  Brown,"  and  during 
1915  by  W.  E.  GilfillanJ  The  data  for  these  two  years  are  of  little 
value  in  themselves,  because  the  numbers  employed  were  relatively 
small.  During  1916  the  work  was  largely  confined  to  the  determina- 
tion of  the  question  of  self-sterility,  and  in  1917  the  same  work  was 
repeated  and  many  cross-pollinations  made.  In  1918  repetition  of  all 
self-pollinations  and  crosses  was  again  made,  but  frost  in  the  Univer- 
sity orchards  at  Davis  and  the  6.  W.  Atterbury  orchard  at  Woodland 
vitiated  the  whole  season's  efforts,  with  the  exception  of  the  experi- 
ments performed  on  the  Nonpariel  variety,  which  were  carried  on  in 
the  orchard  of  Mr.  G.  W.  Pierce,  some  six  miles  distant  from  the 
University  Farm.  The  work  of  1918  was  repeated  during  the  season 
of  1919  in  the  University  orchards  at  Davis. 

With  the  exceptions  noted  all  experiments  were  conducted  in  the 
University  orchards  at  Davis.  The  trees  in  these  orchards  were  all 
young  and  vigorous,  having  been  planted  during  the  spring  of  1908. 
The  Pierce  orchard  was  planted  in  1892  and  the  trees  were  in  fair 
vigor.  In  the  Atterbury  orchard  the  trees  were  young  and  vigorous, 
having  been  planted  in  1914. 

THE    BLOOMING    PERIOD    OF    CERTAIN   ALMOND    VARIETIES 

Almonds  have  a  relatively  long  period  of  bloom  if  the  total  time 
from  the  opening  of  the  first  blossoms  to  the  shedding  of  the  petals 
is  considered.  Many  growers  arc  of  the  opinion  that  even  the  later 
blooming  varieties  overlap  sufiQcii  ntly  with  the  earlier  varieties  to  set 
a  crop  on  the  latter.  Such  a  selection  of  varieties,  however,  is  not 
to  be  generally  advised,  although  in  some  cases  it  may  be  desired  to 
use  a  variety  listed  as  an  early  bloomer  to  pollenize  a  late  bloomer. 
Based  on  what  may  be  called  the  period  of  effective  bloom,  varieties 
may  be  roughly  divided  into  early  and  late  bloomers,  as  shown  in  the 
following  lists.  The  Nonpareil  has  been  included  in  both  lists  as 
being  just  about  midway. 

Early  iloomers  Late  bloomers 

Big  White  Flat      Klondike  Dickinson 

California  Lewelling  Drake 

Eureka  Ne  Plus  Ultra  Golden  State 

Harriott  Nonpareil  Languedoc 

I.  X.  L.  Peerless  Nonpareil 

Jordan  Princess  Reams 

King  Silver  Shell  Sellers 

Texas 

8  Brown,  B.  8.,  Almond  Culture,  a  thesis  presented  in  partial  fulfillment  of 

the  requirements  for  the  Master's  degree  from  the  University  of  California,  1911. 
7  GilfiJlan,  W.  E.,  Pollination  of  the  Almond,  a  thesis  presented   in   partial 

fulfillment  of  the  requirements  for  the  Bachelor's  degree  from  the  University  of 

California,  1915. 


b  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

The  accompanying  chart  (page  7)  gives  the  average  blooming 
seasons  of  certain  almond  varieties  for  the  years  1914  to  1921,  in- 
clusive, unless  otherwise  noted.  The  date  of  bloom  is  of  course 
dependent  on  many  factors,  such  as  soil,  season,  and  location. 


Period   of     Effective   BlojjcinJnfe'  t'f  Almonclj-Univerjity  Rnii -1*517- 

FEBRUARY  *^      MARCH    J_ 


Harriott 

NePliuUltr* 

i.X.L. 

Peerlejj' 

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Prince./ J' 

Lewelling 

California, 

King 

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br«.ke 

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Fig.  1. — The  effective  blooming  period  of  certain  almond  varieties  during  the 
season  of  1917.  The  dates  in  this  table  cover  the  time  each  variety  was  in  con- 
spicuous bloom  and  therefore  of  maximum  attraction  to  insects. 


POLLEN    PRODUCTION    OF   ALMOND    VARIETIES 

In  addition  to  the  inquirj'-  into  the  viability  of  the  pollen  produced 
and  the  date  of  bloom  of  a  certain  variety,  the  orchardist  in  selecting 
a  pollenizer  for  his  commercial  orchard  must  take  into  consideration 
whether  the  variety  to  be  planted  as  a  pollenizer  is  a  good  pollen 
producer.  In  practically  all  instances  the  pollen  production  of  the 
first  almond  blossoms  was  noted  to  be  very  inferior  in  quantity  to 
that  produced  by  flowers  maturing  several  days  later. 

Data  covering  the  abundance  of  pollen  production  have  been 
collected  for  three  seasons.    The  results  are  presented  herewith. 


Pollen  Production  of  Seventeen  Almond  Varieties 


Variety 


Big  White  Flat 

California 

Drake 

Golden  State 

Harriott 

I.  X.  L. 


Pollen  production, 
1917 

Abundant 

Abundant 

Very  abundant 

Abundant 

Abundant 

Abundant 


Pollen  production, 
1918 

Very  abundant 

Very  abundant 

Very  abundant 

Medium  to  shy 

Abundant 

Abundant 


Pollen  production, 
1919 


Abundant 
Very  abundant 


Abundant 
Abundant 


Bulletin  346  J 


ALMOND  POLI/INATION 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Pollen  Production  of  Seventeen  Almond  Varieties — (Continued) 

Variety 

Pollen  production, 
1917 

Pollen  production, 
1918 

Pollen  production. 
1919 

Jordan 

Medium  to 

shy 

Shy 

Shy 

King 

Medium 

Medium 

Abundant 

Klondike 

Abundant 

Medium 

Abundant 

Languedoc 

Very  shy 

Medium  to 

shy 

Medium 

Lewelling 

Abundant 

Medium 

Shy 

Ne  Plus  Ultra 

Abundant 

Abundant 

Medium 

Nonpareil 

Abundant 

Abundant 

Abundant 

Peerless 

Abundant 

Abundant 

Abundant 

Princess 

Abundant 

Abundant 

Shy 

Reams 

Abundant 

Abundant 

Abundant 

Texas 

Medium  to  abundant  Abundant 

Very  abundant 

GERMINABILITY   OF  THE   POLLEN   USED 

The  pollen  used  in  all  experiments  was  in  prime  condition  and 
passed  in  all  cases  a  very  satisfactory  artificial  germination  test.  In 
many  instances  pollen  collected  from  early  maturing  flowers  proved 
to  be  of  very  poor  viability  as  compared  with  that  produced  by  later 
blossoms  on  the  same  tree. 

TABLE  I 

GERMINABILITY   OF   POLLEN,    SEASONS    1915-1919 

Figures  give  per  cent  germination  in  12  per  cent  cane  sugar  solution. 

Variety                               1915  1916  1917  1918                  1919 

Big  White  Flat ....  93  76  75 

California  75  37  77  50 

Dickinson   ....  51                   

Drake    94  35  33  32  13 

Eureka    ....  ....  14  29 

Golden  State  ....  25  32  13 

Harriott    92  76  80  88  50 

I.  X.  L 85  80  94  60  74 

Jordan  73  50  85  64  12 

King  80  33  48  54 

Klondike  ....  89  86  65 

Languedoe    44  28  12  15  29 

Lewelling   88  90  69  65  32 

Ne  Plus  Ultra 89  83  94  74  88 

Nonpareil  90  88  53  44  11 

Peerless  50  24  60  15 

Princess    81  63  39  37  13 

Reams  90  ....  53  25 

Sellers  ....  ....  64  !§ 

Silver  Shell ....  ....  ....  40 

Texas 85  86  60  16 

•  Average 82.1  69.5  57.1  52.8  37.0 


Bulletin  346]  ALMOND  POLLINATION  9 

During  the  first  two  seasons  weather  conditions  during  the  bloom- 
ing period  of  almonds  were  favorable  for  the  setting  of  fruit  and,  as 
a  consequence,  very  high  germination  tests  were  recorded.  During 
1917,  1918,  and  1919,  however,  wind,  cold,  and  rain  destroyed  to  a 
marked  degree  the  viabilitj''  of  the  pollen.  But  inasmuch  as  only  one 
viable  pollen  grain  is  actually  necessary  to  effect  fertilization,  and 
since  by  actual  count  it  was  determined  that  from  sixty  to  one  hun- 
dred and  twenty-five  pollen  grains  were  deposited  on  the  stigma  of 
each  flower  artificially  pollinated,  there  need  be  no  fear  as  to  the 
accuracy  of  the  results  because  of  low  viability  of  the  pollen  employed. 

RELATION    OF   NORMAL   SET   TO    FINAL   CROP 

Immediately  after  the  petals  fall  each  flower  begins  to  form  a  fruit. 
During  the  following  two  or  three  weeks  a  certain  percentage  of  these 
young  fruits  drop  and  only  a  rather  low  percentage  of  the  total 
number  of  original  blossoms  continues  to  develop.  It  is  essential  that 
this  drop  take  place,  as  the  tree  under  average  circumstances  would 
never  be  able  to  carry  so  many  fruits  through  to  maturity.  The  factors 
determining  which  of  these  young  fruits  shall  drop  are  not  at  present 
fully  known.  Later  in  the  season  there  takes  place  still  another  falling 
of  young  fruits  known  as  the  "June  drop." 

The  expression  normal  set  is  a  more  or  less  technical  term  designat- 
ing the  percentage  of  fruit  which  the  tree  sets  under  normal  con- 
ditions when  left  open  to  insect  pollination.  It  is  obvious  that  the 
normal  set  may  be  determined  at  any  time  up  to  the  end  of  the  season 
by  counting  the  fruits  on  a  tree  and  comparing  that  number  with  the 
original  bloom.  In  these  experiments  approximately  2000  blossoms 
of  each  variety,  well  distributed  over  the  trees,  were  counted  each 
year  and  proper  records  kept  to  determine  the  normal  set  after  the 
first  and  the  second  drop,  and  at  harvest  time. 

The  questions  at  once  arise  as  to  what  percentage  of  normal  set  at 
harvest  time  constitutes  a  full  crop  and  what  is  meant  by  a  "full 
crop."  What  constitutes  a  full  crop  of  any  fruit  is  perhaps  largely  a 
question  of  judgment  or  guess.  It  varies  with  such  factors  as  variety, 
soil,  and  moisture  conditions.  What  would  be  considered  a  full  crop 
under  foothill  conditions  would  not  necessarily  be  the  same  in  a 
valley  location.  In  order  to  secure  some  idea  on  this  important  phase 
of  the  subject,  table  II  is  herewith  presented  which  gives  the  normal 
set  of  certain  almond  varieties  for  the  years  1916,  1917,  and  1919, 
together  with  the  average  yield  in  pounds  of  these  trees  reduced  to  an 
acreage  basis.    The  trees  under  observation  were  planted  during  the 


10  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION 

spring  of  1908,  being  set  twenty -four  feet  apart  by  the  square  system, 
which  gives  approximately  seventy-five  trees  to  the  acre.  Since  plant- 
ing, these  trees  have  received  good  commercial  culture.  All  figures 
given  are  based  on  the  yields  of  almonds  harvested. 

A  brief  examination  of  the  table  shows  that  too  much  stress  must 
not  be  laid  on  mere  percentages,  because  during  the  1916  season  the 
normal  set  was  much  heavier  than  in  1917  or  1919,  but  the  crop  of  the 
latter  two  years  was  much  heavier.  This  is  easily  explained  by  the 
relatively  heavier  bloom  during  the  springs  of  1917  and  1919.  These 
figures  also  emphasize  the  importance  of  correct  comparisons  and  show 
that  the  normal  set  must  be  carefully  taken  each  year  in  order  to 
secure  a  correct  basis  for  the  comparison  of  results  obtained  by  arti- 
ficial pollination. 

TABLE  II 

Comparison  of  Normal  Set  with  Yield  of  Almonds  in  Pounds 

(Dry  Weight)  per  Acre 

1916  1917  1919 


Variety 

Percentage 
set 

Lbs.  per 
acre 

Percentage 
set 

Lbs.  pel 
acre 

IPercentage 
set 

Lbs.  per 
acre 

Big  White  Flat 

.... 

13.0 

1,402 

California 

14 

889 

7.3 

865 

3.6 

1,362 

Drake 

15 

1,229 

16.4 

3,800 

15.5 

1,162 

Golden  State 

14.5 

2,775 

Harriott 

16 

893 

11.9 

2,240 

8.4 

1,650 

I.  X.  L. 

17 

1,059 

16.5 

1,515 

21.7 

1,575 

Jordan 

13 

817 

3.6 

455 

0.3 

600 

King 

29 

660 

25.7 

1,395 

26.2 

2,047 

Klondike 

13.2 

1,125 

Languedoe 

22 

1,763 

16.5 

745 

10.9 

1,391 

Lewelling 

37 

1,235 

25.0 

2,035 

29.7 

975 

Ne  Plus  Ultra 

28 

1,714 

20.4 

3,670 

16.9 

1,500 

Nonpareil 

24 

869 

28.2 

2,415 

Peerless 

20 

888 

7.0 

895 

9.0 

1,950 

Princess 

17 

935 

17.7 

1,275 

13.9 

1,905 

Beams 

23 

2,044 

14.0 

2,905 

18.0 

1,950 

Silver  Shell 



10.0 

1,125 

Texas 

39 

1,657 

21.7 

1,430 

39.0 

1,308 

Average  22.3         1,189  16.6  1,885  15.5  1,522 

NORMAL    SET    OF   ALMOND    VARIETIES 

There  is  presented  in  table  III  a  record  of  the  normal  set  of  various 
almond  varieties  under  test  at  the  University  Farm.  It  will  be  noted 
that  the  normal  set  in  the  University  orchards  with  open  pollination 
ranged  all  the  way  from  0.3  per  cent,  in  the  case  of  the  Jordan  in 


Bulletin  346] 


ALMOND  POLLINATION 


11 


1919,  to  39  per  cent,  in  the  case  of  the  Texas,  in  1916  and  1919.  Prob- 
ably due  to  unfavorable  weather  conditions  at  the  time  of  blossoming, 
the  set  during  1917  and  1919  on  the  whole,  was  somewhat  lower  than 
that  of  1916,  the  average  being  15.7  per  cent,  16.6  per  cent,  and  22.3 
per  cent,  in  1919,  1917,  and  1916,  respectively.  On  account  of  the 
heavier  bloom,  however,  the  crop  was  considerably  heavier  in  1917 
than  in  either  1916  or  1919 ;  however,  certain  varieties.  King  for 
example,  produced  a  much  heavier  crop  with  practically  the  same 
percentage  of  blossoms  setting,  in  1919.  Attention  is  also  called  to 
the  fact  that  in  the  orchard  of  ]\Ir.  G.  W.  Pierce  (table  VI)  the  set 
was  considerably  lower  than  at  the  University  Farm.  This  is  ex- 
plained by  the  fact  that  in  Mr.  Pierce's  orchard  practically  no  insect 
pollen  carriers  were  present.  The  orchard  is  properly  inter-planted 
with  pollenizing  varieties. 


TABLE  III 

Normal  Set  op  Fruit  on  Almond  Varieties 
1916,  1917,  1919 
University  Farm,  Davis,  California. 

1916  1917                                         1 

, * X  , ' N  > 

Number     Percentage  Number      Percentage  Number 

blossoms       matured  blossoms         matured  blossoms 

Variety               counted  counted  counted 

Big  White  Flat    ....  1,083             14.2  1,091 

California              2,402             14  2,707               7.3  2,577 

Drake                     2,141             15  2,752             16.4  2,339 

Eureka  ....  336 

Golden  State          ....  1,044            30.0                 1,022 

Harriott                 1,961             16  2,301             11.9  1,175 

I.  X.  L.                  2,131             17  2,663             16.5  2,751 

Jordan                    1,970             13  2,593               3,6  2,534 

King                       1,675             29  2,512             25.7  2,533 

Klondike                1,069             30.4  2,893 

Languedoc            2,294            22  2,488             16.5  3,003 

Lewelling              2,151             37  2,653             25.0  2,190 

Ne  Plus  Ultra      2,071             26  1,953             20.4  2,886 

Nonpareil              1,989             24  2,647             28.2                  

Peerless                 1,975             20  1,925               7.0  2,757 

Princess                 2,085             17  2,731             17.7  2,426 

Sellers  1,279 

SUver  Shell            742             17.7  1,070 

Reams                •    1,910             23  2,001             14.0  2,828 

Texas                     2,019             39  2,568            21.7  2,556 


Percentaee 
matured 

13.0 

3.6 

1.5.5 

16.9 

14.5 

8.4 

21.7 

0.3 

26.2 

13.2 

10.9 

29.7 

16.9 


9.0 
13.9 
17.8 
10.6 
18.0 
39.0 


12 


UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION 


SELF-STERILITY    IN    VARIOUS    ALMOND    VARIETIES 

1916,  1917,  1919 

Table  IV  gives  the  self-pollination  record  of  the  almond  varieties 
tested  for  self-sterility  during  1916,  1917,  and  1919.  From  this  table 
it  will  be  noted  that  all  of  the  twenty  varieties  tested  gave  distinct 
evidence  of  self-sterility.  The  Harriott  variety  in  1916  proved  self- 
fertile,  but  in  1917  and  1919  was  decidedly  self-sterile.  The  probable 
explanation  is  that  this  variety  behaves  like  certain  varieties  of  apples 
and  pears  which  one  season  may  be  self-sterile,  while  another  season 
they  may  be  partlj''  self-fertile.  It  is  possible,  however,  that  this 
variety  was  cross-pollinated  by  mistake  in  1916.  The  results  of  these 
three  seasons — 1916,  1917,  and  1919 — and  also  1910  and  1911  are 
the  same,  viz.,  that  for  all  practical  purposes  the  cultivated  almond 
is  self-sterile  and  in  all  cases  orchards  must  be  inter-planted  with 
pollenizing  varieties  if  they  are  to  prove  commercially  profitable. 


TABLE  IV 

Self-Pollination  of  Almond  Varieties 

1916,  1917,  1919 

University  Farm,  Davis,  California 

1916  1917 


1919 


Variety 

Number 
Blossoms 

Self- 
Pollinated 

Percentage 
Matured 

Number 
Blossoms 

Self- 
Pollinated 

Percentage 
Matured 

Number 
Blossoms 

Self- 
Pollinated 

Percentage 
Matured 

Big  White  Flat 
California 

673 

2.5 

504 

.2 

1586 

.13 

464 

0 

268 

0 

Drake 

996 

.1 

953 

0 

410 

.2 

Eureka 

A  402 

0 

Golden  State 

554 

.4 

Harriott 

939 

15.0 

1189 

.08 

588 

1.3 

I.  X.  L 

740 

.5 

403 

.25 

403 

0 

Jordan 

819 

.2 

597 

0 

299 

0 

King 

450 

0 

900 

0 

448 

0 

Klondike 

404 

.49 

481 

0 

Languedoc 

979 

.1 

625 

0 

557 

.2 

Lewelling 

1031 

.97 

960 

.63 

408 

0 

Ne  Plus  Ultra 

1005 

.6 

327 

.9 

469 

.4 

Nonpareil 

723 

.14 

446 

.22 

P180 

0 

Peerless 

976 

0 

237 

0 

346 

.28 

Princess 

822 

0 

711 

0 

406 

0 

Sellers 

355 
376 

1.4 

Silver  Shell 

0 

Reams 

1064 

0 

1015 

.09 

499 

1.2 

Texas 

1029 

0 

994 

.2 

530 

0 

Note. — A  in 

the  above  table 

indicates  that  the  work  was  done  in  the  Atterbury 

orchard.     P  in 

the  above  table 

indicates 

that  the  work  was 

done  in 

the  Pierce 

orchard. 

Bulletin  346] 


ALMOND  POLLINATION 


13 


CROSSES    BETWEEN    CERTAIN    ALMOND   VARIETIES 

Tables  V  and  VI  give  the  results  of  artificial  cross-pollinations  dur- 
ing the  years  1916,  1917,  1918,  and  1919. 


TABLE  V 

Cboss-Pollination  op  Almond  Varieties 

1916,  1917,  1919 

University  Farm,  Davis,  California. 

1916  1917 


1919 


Variety 

Big  White  Flat 
X  Harriott 

Number 
Blossoms 

Hand- 
Pollinated 

Number 
Blossoms 
Percentage       Hand- 
Matured      Pollinated 

Percentage 
Matured 

Number 
Blossoms 

Hand- 
Pollinated 

523 

486 

408 

482 
366 
477 
484 
423 

438 
436 
478 
466 
477 
422 
422 
425 
470 

359 
458 

248 
294 

376 
329 
274 

PercentaK( 
Matured 

5,9 

X  Ne  Plus  Ultra 

1  4 

California 
X  Drake 

3.3 

5.8 
3.9 

12.8 
8.2 

24.6 

25  5 

X  I.  X.  L. 

211 

25.9 

X  Jordan 

258 

8.4 

X  Ne  Plus  Ultra 

257 

6.2 

X  Nonpareil 

'250 

208 

30.9 

X  Peerless 

3.0 

Drake 

X  California 

505 

29.4 

X  Eureka 

11.9 

X  I.  X.  L. 

514 

15.1 
24.6 
14.6 
22.8 
16.0 
17.5 
20.0 

19.8 

X  Jordan 

274 

16.0 

X  Languedoc 

499 

980 

450 

502 

14.6 

X  Ne  Plus  Ultra 
X  Nonpareil 
X  Peerless 

28.9 
22.2 
21.1 

X  Texas 

511 

26.4 

Eureka  (A) 
X  Drake 

14.7 

X  Nonpareil 

15.3 

Golden  State 
X  Drake 

35.9 

X  Nonpareil 

38.4 

Harriott 

X  Big  White  Flat 

30.8 

X  I.  X.  L. 

14.6 

23.4 

X  Ne  Plus  Ultra 

568 

24.8 

Note. — (A)   in  the  above  table  indicates  that  crosses  thus  marked  were  per- 
formed in  the  G.  W.  Atterbury  orchard,  Woodland,  California. 


14 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


TABLE  V— (Continued) 
1916  1917 


1919 


Variety 

/.  X.  L. 
X  Drake 

Number 
Blossoms 

Hand-       Percentage 
Pollinated      Matured 

Number 
Blossoms 

Hand- 
Pollinated 

145 

Percentage 
Matured 

1.4 

2.7 
5.6 

Number 
Blossoms 

Hand- 
Pollinated 

413 
364 
327 

Percentage 
Matured 

9  6 

X  California 

21.9 

X  Jordan 

264 
137 

37  4 

X  Lewelling 
X  Harriott 

352 
375 
411 
413 

220 
242 
225 
480 

14  8 

X  Ne  Plus  Ultra 
X  Nonpareil 
X  Peerless 

342          40.0 

484               .8 

343 
412 
404 

165 

139 
183 
179 
227 

6.6 

0 

3.0 

0.6 
3.6 
0 

1.7 
.9 

9.8 
0 
23.2 

Jordan 

X  California 

■  3  8 

X  I.  X.  L. 

3  8 

X  Ne  Plus  Ultra 

5  7 

X  Nonpareil 
X  Peerless 

4  8 

King 

X  Ne  Plus  Ultra 

331 
100 

384 

497 
265 
276 
413 
348 
558 
292 
337 
433 

540 

442 
486 
175 

450 

41  6 

X  Nonpareil 

Klondike 

X  Ne  Plus  Ultra 

32  0 

12.9 
14.9 

14  8 

Languedoc 
X  California 

502 

429 

17  9 

X  Drake 

11.7 

X  Eureka 

16.9 

X  I.  X.  L. 

467 
514 
471 
457 
475 
450 

5.4 
9.7 
4.9 
11.8 
7.6 
0 

9  9 

X  Ne  Plus  Ultra 

8.6 

X  Nonpareil 
X  Peerless 

10.5 

4.4 

X  Reams 

10.3 

X  Texas 
Lewelling 
X  California 

0 
10.9 

X  I.  X.  L. 

424 
373 
244 

P308 

252 

266 

P477 

P160 

6.6 
6.4 
7.5 

7.8 

4.4 

9.7 

18.4 

12.5 

8.4 
12.5 

crosses  thi 

28.0 

X  Ne  Plus  Ultra 
X  Nonpareil 
Ne  Plus  Ultra 
X  California 
X  Drake 

20.9 
29.1 

10.4 

X  Harriott 

580 

P478 

325 

94 

379 

404 

104 

IS  marked 

36.0 

X  L  X.  L. 
X  Jordan 
X  King 
X  Lewelling 
X  Nonpareil 
X  Peerless 

492          36.0 

31.0 
21.5 
19.1 

287 
223 

12.9 

482           17.0 

23.0 
9.6 

Note.—CP)  in 

the  above  table  indicates  that 

were  per- 

Bulletin  346] 


ALMOND  POLLINATION 


15 


TABLE  Y— (Continued) 
1916  1917 


1919 


Variety 
Nonpareil 

Number 
Blossoms 

Hand- 
Pollinat«d 

Number 
Blossoms 
Percentage        Hand- 
Matured      Pollinated 

Percentage 
Matured 

Number 
Blossoms 

Hand- 
Pollinated 

Percentage 
Matured 

X  I.  X.  L. 

484 

.17          283 

.4 

X  Jordan 

401 

16.2 
22  1 

X  Lewelling 

258 

X  Ne  Plus  Ultra 

402 

26.0         

486 

520 

25  9 

X  Peerless 

12  0 

X  Texas 

500 

22  4 

Peerless 

X  California 

540 

4  8 

X  Drake 

394 

11  1 

X  Eureka 

439 

6.3 

X  I.  X.  L. 

421 

2.8 

X  Jordan 

447 

7  7 

X  Languedoc 

245 

11  8 

X  Ne  Plus  Ultra 

427 
407 

9  1 

X  Nonpareil 

6.3 

X  Texas 

428 

10  7 

Princess 

X  Ne  Plus  Ultra 

324 
223 

16  8 

X  Nonpareil 
Reams 

26  0 

X  California 

306 

16  7 

458 

20  3 

X  Drake 

516 

27  1 

X  I.  X.  L. 

66 

21.2 

X  Languedoc 
X  Ne  Plus  Ultra 

453 

22  9 

497 

19.5 

239 

18.9 

X  Nonpareil 

502 

18.5 

370 

27.6 

X  Texas 

509 

26.7 

460 

31  0 

Sellers 

X  Drake 

324 

245 

11.1 

X  Nonpareil 

saver  Shell 

23  4 

X  Drake 

438 

17,1 

Texas 

X  California 

528 

8.9 
16.5 

596 
364 
456 

24  7 

X  Drake 

478 

26  3 

X  Eureka 

22.8 

X  L  X.  L. 

394 

19.6 

228 

27.1 

X  Languedoc 

499 

0 

505 

0 

X  Ne  Plus  Ultra 

418 

31.5 

X  Nonpareil 
X  Peerless 

557 

17.8 

323 

26.3 

339 
221 

11  5 

X  Reams 

31.3 

16 


UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION 


Variety 

Nonpareil 
Normal  Set 
Self-pollinated 
California 
Drake 
Eureka 
Golden  State 
I.  X.  L. 
Jordan 
Languedoc 
Ne  Plus  Ultra 
Peerless 
Texas 


TABLE  VI 

Crosses  on  Nonpareil  Almond 

1917,  1918,  1919 

G.  W.  Pierce  orchard,  near  Davis,  California 

1917                                  1918  1919 

Number                              Number  Number 

Blossoms                            Blossoms  Blossoms 

Hand-        Percentage       Hand-  Percentage  Hand-  Percentage 

Pollinated      Matured      Pollinated  Matured  Pollinated  Matured 

3346     2.8    2633  1.5  2067  6.8 

572     0  .      356  0  180  0 

392    35.7     348  7.7  514  25.0 

366    12.7     370  22.0  566  34.1 

259  8.8  375  37.6 

292  20.2  

237     0      801  0  411  0 

226  9.7  305  30.1 

477  23.9  241  31.2 

406    12.5     320  24.3  486  25.9 

396    15.8     322  15.9  520  12.0 

212    29.7     409  21.2  500  22.4 


INTER-STERILITY    BETWEEN    ALMOND   VARIETIES 

In  all  the  reciprocal  crosses  made,  only  the  I.  X.  L.  and  Nonpareil, 
and  the  Languedoc  and  Texas  varieties  seemed  to  give  distinct  evidence 
of  inter-sterility.  These  cases  of  inter-sterility  have  never  before  been 
recorded,  so  far  as  the  writers  know.  The  inter-sterility  between 
I.  X.  L.  and  Nonpareil  has  been  experimentally  proved  in  1915,  1916, 
1917,  1918,  and  1919  and  has  also  been  experienced  in  practice  by 
many  growers;  the  inter-sterility  between  Languedoc  and  Texas  was 
experimentally  proved  in  1917  and  1919. 

The  parentage  of  almond  varieties  at  present  grown  in  California 
is  unknown  and  it  is  therefore  impossible  to  attempt  an  explanation 
of  the  inter-sterility  of  these  varieties  on  the  basis  of  relationships. 


INFLUENCE   OF   POLLENIZERS   ON   CERTAIN   ALMOND  VARIETIES 

During  the  season  of  1916  reciprocal  crosses  were  made  only 
between  the  Nonpareil,  I.  X.  L.,  and  Ne  Plus  Ultra  varieties  and  the 
results  showed  the  first  two  to  be  not  only  self-sterile,  but  also  inter- 
sterile,  i.e.,  unable  to  pollinate  themselves  or  each  other.  The  Ne  Plus 
Ultra  fertilized  the  other  two  and  was  in  turn  successfully  fertilized 
by  them. 


Bulletin  346]  almond  pollination  17 

More  than  50,000  artificial  cross-pollinations  were  made  during 
each  of  the  seasons  of  1917,  1918,  and  1919.  As  stated,  the  entire  work 
of  the  1918  season  was  lost  through  frost  except  the  crosses  on  the 
Nonpareil.  Likewise  on  account  of  unfavorable  weather  conditions, 
rather  negative  results  were  obtained  with  certain  varieties  during 
1917.  For  the  sake  of  brevity,  much  of  the  data  collected  is  omitted, 
only  sufficient  being  given  to  prove  each  point.  It  is  felt  that  sufficient 
work  has  been  done  to  give  exact  information  regarding  the  planting 
of  orchards  to  insure  safe  pollination  for  the  more  important  varieties 
of  almonds.  The  investigation  of  this  problem  has  been  confined 
neither  to  the  varieties  at  present  recommended  for  planting  nor  to 
those  now  grown  commercially  in  the  state,  a  consideration  of  several 
kinds  of  minor  importance  having  also  been  included.  In  making 
recommendations  of  varieties  for  interplanting,  the  writers  have 
attempted  to  keep  in  mind  the  date  of  blooming,  abundance  of  pollen, 
and  to  a  limited  extent,  the  productiveness  and  commercial  value  of 
the  pollenizer.* 

Big  White  Flat. — The  Harriott  is  the  best  poUenizer  for  the  Big 
White  Flat. 

California. — The  Nonpareil  is  the  best  pollenizer  for  the  California. 
The  I.  X.  L.  and  Drake  also  are  good  pollenizers  for  the  California. 

Drake. — Nine  varieties  in  all  were  used  as  pollenizers  for  the 
Drake.  These  varieties  were  the  California,  Eureka,  I.  X.  L.,  Jordan, 
Languedoc,  Ne  Plus  Ultra,  Nonpareil,  Peerless,  and  Texas.  Prefer- 
ence should  be  given  to  the  California,  Ne  Plus  Ultra,  Nonpareil,  and 
Texas  varieties. 

Eureka. — The  Drake  and  Nonpareil  are  satisfactory  pollenizers  for 
the  Eureka. 

Golden  State. — The  Drake  and  Nonpareil  are  satisfactory  pollen- 
izers for  the  Golden  State. 

Harriott. — The  I.  X.  L.  and  Ne  Plus  Ultra  are  good  pollenizers  for 
the  Harriott. 

I.  X.  L. — The  Ne  Plus  Ultra  is  a  satisfactory  pollenizer  for  the 
I.  X.  L.  Nonpareil  failed  in  all  three  years  to  set  fruit  on  the  I.  X.  L. 
:  California,  Jordan,  and  Peerless  may  be  used  as  pollenizers  for  the 
I.  X.  L. 

Jordan. — No  especially  good  pollenizer  has  been  found  for  the 
Jordan,  which  is  notoriously  a  shy  bearer.  Ne  Plus  Ultra  and  Non- 
pareil give  fairly  good  results  as  pollenizers. 

8  The  reader  will  find  a  comprehensive  discussion  of  the  proper  varieties  for 
the  commercial  plantation  in  Taylor's  "The  Almond  in  California,"  Bull.  No. 
297,  Calif.  Exp.  Station. 


18 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


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Bulletin  346] 


ALMOND  POLLINATION 


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22  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

King. — The  King  may  be  successfully  pollenized  with  the  Ne  Plus 
Ultra  and  Nonpareil  varieties. 

Kloivdike. — The  Ne  Plus  Ultra  may  be  used  to  pollenize  the  Klon- 
dike. 

Lcmguedoc. — Of  the  nine  sorts  of  pollen  used  to  cross  with  the 
Languedoc,  that  of  the  California,  Drake,  and  Eureka  varieties  yielded 
the  best  results.  The  Texas  is  the  only  variety  which  failed  to  set 
fruit  on  the  Languedoc.  From  the  standpoint  of  the  blooming  season 
the  Drake  should  probably  be  recommended  as  a  pollenizer. 

Lemelling. — The  I.  X.  L.,  Ne  Plus  Ultra,  and  Nonpareil  may  be 
recommended  as  pollenizers  for  the  Lewelling. 

Ne  Plus  Ultra. — Of  the  nine  varieties  of  pollen  used  to  cross  with 
the  Ne  Plus  Ultra,  the  following  gave  the  best  results :  I.  X.  L.,  Jordan, 
Nonpareil.  From  a  commercial  standpoint  the  I.  X.  L.  and  Nonpareil 
should  be  given  preference. 

Nonpareil. — Of  the  eleven  varieties  tested  as  pollenizers  for  the 
Nonpareil  only  the  I.  X.  L.  failed  to  set  fruit.  The  following  varieties 
proved  to  be  successful  pollenizers :  California,  Drake,  Eureka, 
Languedoc,  Ne  Plus  Ultra,  Peerless,  and  Texas.  Preference  should  be 
given  to  the  California,  Drake,  Ne  Plus  Ultra,  and  Texas. 

Peerless. — Of  the  nine  varieties  used  as  pollenizers  for  the  Peerless, 
the  Drake,  Languedoc,  and  Texas  proved  to  be  the  best. 

Princess. — The  Nonpareil  and  Ne  Plus  Ultra  may  be  used  to  pollen- 
ize the  Princess. 

Reams. — California,  I.  X.  L.,  Ne  Plus  Ultra,  Nonpareil,  Texas,  and 
Drake  gave  entirely  satisfactory  results  as  pollenizers  for  the  Reams. 
The  Texas  should  be  given  preference. 

Sellers. — The  Nonpareil  is  a  satisfactory  pollenizer  for  the  Sellers. 

Silver  Shell. — The  Drake  may  be  recommended  as  a  pollenizer  for 
the  Silver  Shell. 

Texas. — The  following  varieties  may  be  used  to  pollenize  the  Texas : 
Drake,  Eureka,  I.  X.  L.,  Ne  Plus  Ultra,  Nonpareil,  and  Reams.  From 
the  standpoint  of  the  blooming  season,  preference  should  be  given  to 
the  Reams,  Drake,  and  Eureka.  The  Ijanguedoc  failed  to  set  any 
fruit  on  the  Texas. 
I 

POLLENIZING   AGENCIES 

After  having  planted  inter-fertile  varieties  the  orchardist  should, 
by  all  means,  provide  an  agency  for  the  transfer  of  the  pollen  from* 
the  trees  of  one  variety  to  those  of  another.    The  common  honey  bee 
is  by  far  the  best  carrier  of  pollen  and  it  will  pay  the  grower  to  keep 
bees  although  he  may  not  care  to  go  into  the  honey  business.    Bees, 


Bulletin  346]  ALMOND  POLLINATION  23 

however,  are  a  very  profitable  side  line  for  the  orehardist,  espeeially 
if  alfalfa  fields  are  available  after  the  blooming  season  of  fruit  has 
passed.  About  one  hive  of  bees  to  an  aere  of  bearing  orchard  should 
be  provided.  Preferably  the  hives  should  be  scattered  as  widely  as 
possible  throughout  the  orchard  during  the  blooming  season.  Experi- 
ments and  experience  have  shown  that  little  reliance  can  be  placed 
on  the  efficacy  of  wind  and  insects,  other  than  the  honey  bee,  in 
effecting  the  transfer  of  pollen  from  tree  to  tree,  or,  indeed,  from 
flower  to  flower. 

Eliminating  from  consideration  all  conditions  which  may  influence 
the  fruitfulness  of  an  orchard  except  those  occurring  at  blooming  time, 
it  may  be  said  that  the  set  is  largely  influenced  by  weather  conditions 
at  time  of  blooming.  Cold  weather,  aside  from  killing  the  blossoms 
or  lowering  the  vitality  of  the  pollen,  often  prevents  bees  from  work- 
ing. The  same  would  be  true  if  cloudy,  wet,  and  windy  weather 
prevail.  For  their  best  work  bees  demand  clear,  warm,  and  quiet 
days  and  since  the  weather  at  the  time  almonds  bloom  is  often  quite 
unsettled,  it  is  readily  seen  that  the  blooming  period  of  the  various 
pollenizing  varieties  should  overlap  perhaps  a  week  in  order  that 
there  may  be  one  or  two  days  at  least  when  the  weather  will  be  favor- 
able for  insect  pollination. 

As  a  case  in  point  mention  may  be  made  of  the  1917  blooming 
season  of  almonds.  Many  almond  growers  had,  during  that  season,  a 
light  crop — due  not  to  lack  of  proper  varieties,  nor  to  freezing  cold, 
but  to  the  existence  of  unfavorable  weather  conditions  throughout  the 
blooming  period  so  that  the  bees  were  prevented  from  working.  This 
point  further  illustrates  the  necessity  of  having  in  the  orchard  a 
large  number  of  these  "helpers." 

ARRANGEMENT   OF  THE   ORCHARD   FROM   A    POLLINATION    STANDPOINT 

In  planting  an  orchard  it  is  desirable  to  have  at  least  every  sixth 
and  preferably  every  fourth  row  of  a  pollenizing  variety.  For  con- 
venience in  harvesting,  it  is  best  to  plant  two  rows  of  one  kind,  then 
two  rows  of  the  pollenizing  variety,  and  so  on ;  or,  if  it  is  desired  to 
have  more  of  one  variety  than  another,  four  rows  of  the  favored 
variety  and  then  two  rows  of  the  pollenizer,  and  repeat.  For  various 
reasons,  it  is  often  desirable  to  reduce  the  number  of  pollenizing  trees 
to  the  minimum.  Under  these  circumstances,  one  tree  in  twenty-flve 
is  perhaps  sufficient,  although  at  least  one  tree  in  eight  is  strongly 
recommended.  It  is  seldom  wise  to  graft  over  a  part  of  a  tree  to  the 
pollenizing  variety  as  this  tends  toward  confusion  and  expense  in 
harvesting. 


24  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

In  planting  one  tree  of  the  pollenizer  to  seven  or  eight  of  the  main 
variety,  the  pollenizer  should  be  placed  as  every  third  tree  in  every 
third  row  in  sucli  a  way  that  the  spaces  in  the  pollination  rows  are 
broken,  as  shown  in  diagram  below,  the  ' '  0  "  in  each  case  representing 
a  pollenizer  tree. 

If  by  chance  a  self -sterile  variety  has  been  planted  in  a  solid  block, 
the  necessary  pollinator  may  be  introduced  by  grafting.  Some  relief 
may  be  obtained  during  the  years  while  waiting  for  the  trees  grafted 
over  to  pollenizing  varieties  to  come  into  bearing,  by  cutting  off  large 
limbs  of  pollenizing  varieties,  placing  the  cut  ends  in  buckets  of  water 
and  distributing  them  throughout  the  orchard  during  the  blooming 
period.  Such  limbs  will  live  for  several  days  and  continue  to  bloom, 
forming  pollen  for  the  bees  to  transfer  to  the  self-sterile  variety. 


SUMMARY   OF   ALMOND    POLLINATION 

1.  Almond  varieties  may  be  roughly  divided  into  two  classes, 
early  bloomers  and  late  bloomers,  when  the  length  of  their  effective 
full  bloom  is  considered. 

2.  The  first  blossoms  produced  by  most  almond  varieties  each 
season  may  yield  a  smaller  amount  of  pollen  and  pollen  which  is 
inferior  in  viability  to  that  produced  by  flowers  on  the  same  tree 
maturing  several  days  or  a  week  later. 

3.  Pollenizing  agencies,  such  as  the  honey  bee,  are  necessary  to 
the  set  of  a  good  crop  of  fruit.  One  colonj^  of  honey  bees  should 
be  provided  for  each  acre  of  orchard. 


Bulletin  346]  ALMOND  POLUNATION  25 

4.  All  almond  varieties  thus  far  tested  have  proved  self-sterile,  at 
least  in  certain  years.  All  of  the  twenty  varieties  tested  during  the 
seasons  of  1917  and  1919  proved  self-sterile.  This  list  includes  the 
Big  White  Flat,  California,  Drake,  Eureka,  Golden  State,  Harriott, 
I.  X.  L.,  Jordan,  King,  Klondike,  Languedoc,  Lewelling,  Ne  Plus 
Ultra,  Nonpareil,  Peerless,  Princess,  Sellers,  Silver  Shell,  Reams, 
Texas,  and  a  hardshell  seedling. 

5.  The  I.  X.  Ij.  and  Nonpareil  varieties  proved  practically  inter- 
sterile  during  three  seasons'  work. 

6.  The  Languedoc  and  Texas  proved  practically  inter-sterile  as 
shown  by  the  results  of  1917  and  1919, 

7.  The  California,  disregarding  its  own  commercial  value,  at  pres- 
ent seems  to  be  the  one  best  pollenizer  for  all  varieties  thus  far  tested, 
which  have  a  coincident  period  of  bloom, 

8.  The  Big  White  Flat  may  be  pollinated  by  the  Harriott. 
The  Calif  omia  may  be  pollinated  by  the  Nonpareil  and  Drake. 
The  Drake  may  be  pollinated  by  the  California,  Ne  Plus  Ultra, 

Nonpareil,  and  Texas. 

The  Eureka  may  be  pollinated  by  the  Nonpareil  and  Drake. 

The  Golden  State  may  be  pollinated  by  the  Drake  and  Nonpareil. 

The  Harriott  may  be  pollinated  by  the  Ne  Plus  Ultra. 

The  /.  X.  L.  may  be  pollinated  by  the  Ne  Plus  Ultra. 

The  Jordan  may  be  pollinated  by  the  I.  X.  L.  and  Nonpareil. 

The  KiTig  may  be  pollinated  by  the  Ne  Plus  Ultra  and  Non- 
pareil. 

The  Klondike  may  be  pollinated  by  the  Ne  Plus  Ultra. 

The  Languedoc  may  be  pollinated  by  the  Drake, 

The  Lewelling  may  be  pollinated  by  the  I.  X.  L.,  Ne  Plus  Ultra, 
and  Nonpareil. 

The  Ne  Plu^  Ultra  may  be  pollinated  by  the  California,  I.  X.  L., 
Jordan,  and  Nonpareil. 

The  Nonpareil  may  be  pollinated  by  the  California,  Drake,  Jor- 
dan, Ne  Plus  Ultra,  Peerless,  and  Texas. 

The  Peerless  may  be  pollinated  by  the  Drake,  Languedoc,  and 
Texas. 

The  Princess  may  be  pollinated  by  the  Ne  Plus  Ultra  and  Non- 
pareil. 

The  Reams  may  be  pollinated  by  the  Texas, 

The  Sellers  may  be  pollinated  by  the  Drake  and  Nonpareil. 


26  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

The  Silver  Shell  may  be  pollinated  by  the  Drake. 
The  Texas  may  be  pollinated  by  the  Drake  and  Nonpareil. 
9.  Care  should  be  taken  in  the  arrangement  of  varieties  in  the 
orchard  to  facilitate  cross-pollination  and  convenience  in  harvesting. 

ACKNOWLEDGMENTS 

The  writers  wish  to  express  their  appreciation  of  the  assistance 
they  received  from  students  and  colleagues.  Messrs.  M.  B.  Weidenthal 
and  Henry  Schlapp,  senior  students  in  the  University  of  California, 
performed  certain  phases  of  the  work  as  thesis  problems,  and  without 
their  help  it  would  have  been  impossible  to  make  so  many  pollinations. 
Mr.  M.  N.  Wood,  Miss  Edna  Euss,  and  Miss  R.  M.  Amesbury,  mem- 
bers of  the  Division  of  Pomology,  also  rendered  invaluable  assistance 
in  the  field  and  laboratory.  Mr.  W.  L.  Howard  has  given  great  service 
in  suggestions  and  criticisms.  Mr.  George  "W.  Pierce  and  Mr.  G.  W, 
Atterbury  kindly  allowed  the  use  of  their  orchards  for  certain  experi- 
ments which  could  not  be  carried  out  in  the  University  orchards. 


Bulletin  346] 


ALMOND  POLLINATION 


27 


Fig.  7. — Only  two  Nonpareil  fruits  from  349  blossoms  left  open  to  natural 
conditions  (normal  set).  Only  that  portion  of  the  branch  bearing  fruit  is  shown 
in  the  photograph.    A  typical  example  of  the  normal  set  in  the  Pierce  orchard,  1918. 


28 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


Fig.  8. — No  fruit  set  on  branch  of  Nonpareil  which  was  pollinated  with  its 
own  pollen.  Twenty-eight  blossoms  set  no  fruit.  A  typical  cluster  of  Nonpareil 
when  self-pollinated.     Pierce  orchard,  1918. 


Bulletin  34(?] 


ALMOND  POLLiINATION 


29 


Fig.  9. — Six  Nonpareil  fruits  set  from  fifteen  blossoms  pollinated  with  Califor- 
nia pollen.  A  typical  cluster  resulting  from  crossing  Nonpareil  with  California. 
Pierce  orchard,  1918. 


30  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Fig.  10. — Twelve  Nonpareil  fruits  set  from  thirty-one  blossoms  pollinated 
with  Golden  State  pollen.  A  typical  cluster  resulting  from  crossing  Nonpareil 
with  Golden  State.     Pierce  orchard,  1918. 


Bulletin  346] 


ALMOND  POLLINATION 


31 


Fig.  11. — No  fruits  set  on  branch  of  Nonpareil  Avhich  was  pollinated  with 
I.  X.  L.  pollen.  Fifteen  blossoms  set  no  fruit.  A  typical  cluster  resulting  from 
crossing  Nonpareil  with  I.  X.  L.    Pierce  orchard,  1918, 


32 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Fig.  12. — Fifteen  Nonpareil  fruits  set  from  twenty-eight  blossoms  pollinated 
with  Languedoc  pollen.  A  typical  cluster  resulting  from  crossing  Nonpareil  with 
Languedoc.     Pierce  orchard,  1918. 


Bulletin  346] 


ALMOND  POLLINATION 


33 


Fig.  13. — Fourteen  Nonpareil  fruits  set  from  twenty-nine  blossoms  pollinated 
with  Ne  Plus  Ultra  pollen.  A  typical  cluster  resulting  from  crossing  Nonpareil 
with  Ne  Plus  Ultra.     Pierce  orchard,  1918. 


k 


34  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


Fig.  14. — Nine  Nonpareil  fruits  set  from  twenty  blossoms  pollinated  with 
Peerless  pollen.  A  typical  cluster  resulting  from  crossing  Nonpareil  with  Peerless. 
Pierce  orchard,  1918. 


Bulletin  346] 


ALMOND  POLLINATION 


35 


Fig.  15. — Twelve  Nonpareil  fruits  set  from  twenty-nine  blossoms  pollinated 
with  Texas  pollen.  A  typical  cluster  resulting  from  crossing  Nonpareil  with 
Texas.     Pierce  orchard,  1918. 


235278 


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